[PATCH 0/3] Convert vmcore to use an iov_iter

[PATCH 0/3] Convert vmcore to use an iov_iter

[Matthew Wilcox (Oracle)]

For some reason several people have been sending bad patches to fix
compiler warnings in vmcore recently.  Here's how it should be done.
Compile-tested only on x86.  As noted in the first patch, s390 should
take this conversion a bit further, but I'm not inclined to do that
work myself.

Matthew Wilcox (Oracle) (3):
  vmcore: Convert copy_oldmem_page() to take an iov_iter
  vmcore: Convert __read_vmcore to use an iov_iter
  vmcore: Convert read_from_oldmem() to take an iov_iter

 arch/arm/kernel/crash_dump.c     |  14 +---
 arch/arm64/kernel/crash_dump.c   |  14 +---
 arch/ia64/kernel/crash_dump.c    |  12 +--
 arch/mips/kernel/crash_dump.c    |  13 +---
 arch/powerpc/kernel/crash_dump.c |  20 +----
 arch/riscv/kernel/crash_dump.c   |  13 +---
 arch/s390/kernel/crash_dump.c    |  12 +--
 arch/sh/kernel/crash_dump.c      |  15 +---
 arch/x86/kernel/crash_dump_32.c  |  13 +---
 arch/x86/kernel/crash_dump_64.c  |  31 ++++----
 fs/proc/vmcore.c                 | 130 +++++++++++++------------------
 include/linux/crash_dump.h       |  19 ++---
 12 files changed, 112 insertions(+), 194 deletions(-)

-- 
2.33.0

[PATCH 1/3] vmcore: Convert copy_oldmem_page() to take an iov_iter

[Matthew Wilcox (Oracle)]

Instead of passing in a 'buf' and 'userbuf' argument, pass in an iov_iter.
s390 needs more work to pass the iov_iter down further, or refactor,
but I'd be more comfortable if someone who can test on s390 did that work.

It's more convenient to convert the whole of read_from_oldmem() to
take an iov_iter at the same time, so rename it to read_from_oldmem_iter()
and add a temporary read_from_oldmem() wrapper that creates an iov_iter.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 arch/arm/kernel/crash_dump.c     | 14 ++-------
 arch/arm64/kernel/crash_dump.c   | 14 ++-------
 arch/ia64/kernel/crash_dump.c    | 12 ++------
 arch/mips/kernel/crash_dump.c    | 13 ++------
 arch/powerpc/kernel/crash_dump.c | 20 +++---------
 arch/riscv/kernel/crash_dump.c   | 13 ++------
 arch/s390/kernel/crash_dump.c    | 12 +++++---
 arch/sh/kernel/crash_dump.c      | 15 +++------
 arch/x86/kernel/crash_dump_32.c  | 13 ++------
 arch/x86/kernel/crash_dump_64.c  | 24 ++++++---------
 fs/proc/vmcore.c                 | 53 ++++++++++++++++++++------------
 include/linux/crash_dump.h       |  9 +++---
 12 files changed, 79 insertions(+), 133 deletions(-)

diff --git a/arch/arm/kernel/crash_dump.c b/arch/arm/kernel/crash_dump.c
index 53cb92435392..15d7db782f24 100644
--- a/arch/arm/kernel/crash_dump.c
+++ b/arch/arm/kernel/crash_dump.c
@@ -27,9 +27,8 @@
  * @buf. If @buf is in userspace, set @userbuf to %1. Returns number of bytes
  * copied or negative error in case of failure.
  */
-ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
-			 size_t csize, unsigned long offset,
-			 int userbuf)
+ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,
+			 size_t csize, unsigned long offset)
 {
 	void *vaddr;
 
@@ -40,14 +39,7 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
 	if (!vaddr)
 		return -ENOMEM;
 
-	if (userbuf) {
-		if (copy_to_user(buf, vaddr + offset, csize)) {
-			iounmap(vaddr);
-			return -EFAULT;
-		}
-	} else {
-		memcpy(buf, vaddr + offset, csize);
-	}
+	csize = copy_to_iter(vaddr + offset, csize, iter);
 
 	iounmap(vaddr);
 	return csize;
diff --git a/arch/arm64/kernel/crash_dump.c b/arch/arm64/kernel/crash_dump.c
index 58303a9ec32c..991d30aac439 100644
--- a/arch/arm64/kernel/crash_dump.c
+++ b/arch/arm64/kernel/crash_dump.c
@@ -25,9 +25,8 @@
  * @buf. If @buf is in userspace, set @userbuf to %1. Returns number of bytes
  * copied or negative error in case of failure.
  */
-ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
-			 size_t csize, unsigned long offset,
-			 int userbuf)
+ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,
+			 size_t csize, unsigned long offset)
 {
 	void *vaddr;
 
@@ -38,14 +37,7 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
 	if (!vaddr)
 		return -ENOMEM;
 
-	if (userbuf) {
-		if (copy_to_user((char __user *)buf, vaddr + offset, csize)) {
-			memunmap(vaddr);
-			return -EFAULT;
-		}
-	} else {
-		memcpy(buf, vaddr + offset, csize);
-	}
+	csize = copy_to_iter(vaddr + offset, csize, iter);
 
 	memunmap(vaddr);
 
diff --git a/arch/ia64/kernel/crash_dump.c b/arch/ia64/kernel/crash_dump.c
index 0ed3c3dee4cd..bc331272bbd6 100644
--- a/arch/ia64/kernel/crash_dump.c
+++ b/arch/ia64/kernel/crash_dump.c
@@ -31,21 +31,15 @@
  * copying the data to a pre-allocated kernel page and then copying to user
  * space in non-atomic context.
  */
-ssize_t
-copy_oldmem_page(unsigned long pfn, char *buf,
-		size_t csize, unsigned long offset, int userbuf)
+ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,
+		size_t csize, unsigned long offset)
 {
 	void  *vaddr;
 
 	if (!csize)
 		return 0;
 	vaddr = __va(pfn<<PAGE_SHIFT);
-	if (userbuf) {
-		if (copy_to_user(buf, (vaddr + offset), csize)) {
-			return -EFAULT;
-		}
-	} else
-		memcpy(buf, (vaddr + offset), csize);
+	csize = copy_to_iter(vaddr + offset, csize, iter);
 	return csize;
 }
 
diff --git a/arch/mips/kernel/crash_dump.c b/arch/mips/kernel/crash_dump.c
index 2e50f55185a6..926665c798b6 100644
--- a/arch/mips/kernel/crash_dump.c
+++ b/arch/mips/kernel/crash_dump.c
@@ -15,8 +15,8 @@
  * Copy a page from "oldmem". For this page, there is no pte mapped
  * in the current kernel.
  */
-ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
-			 size_t csize, unsigned long offset, int userbuf)
+ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,
+			 size_t csize, unsigned long offset)
 {
 	void  *vaddr;
 
@@ -24,14 +24,7 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
 		return 0;
 
 	vaddr = kmap_local_pfn(pfn);
-
-	if (!userbuf) {
-		memcpy(buf, vaddr + offset, csize);
-	} else {
-		if (copy_to_user(buf, vaddr + offset, csize))
-			csize = -EFAULT;
-	}
-
+	csize = copy_to_iter(vaddr + offset, csize, iter);
 	kunmap_local(vaddr);
 
 	return csize;
diff --git a/arch/powerpc/kernel/crash_dump.c b/arch/powerpc/kernel/crash_dump.c
index 5693e1c67c2b..541bcc01490c 100644
--- a/arch/powerpc/kernel/crash_dump.c
+++ b/arch/powerpc/kernel/crash_dump.c
@@ -68,18 +68,6 @@ void __init setup_kdump_trampoline(void)
 }
 #endif /* CONFIG_NONSTATIC_KERNEL */
 
-static size_t copy_oldmem_vaddr(void *vaddr, char *buf, size_t csize,
-                               unsigned long offset, int userbuf)
-{
-	if (userbuf) {
-		if (copy_to_user((char __user *)buf, (vaddr + offset), csize))
-			return -EFAULT;
-	} else
-		memcpy(buf, (vaddr + offset), csize);
-
-	return csize;
-}
-
 /**
  * copy_oldmem_page - copy one page from "oldmem"
  * @pfn: page frame number to be copied
@@ -93,8 +81,8 @@ static size_t copy_oldmem_vaddr(void *vaddr, char *buf, size_t csize,
  * Copy a page from "oldmem". For this page, there is no pte mapped
  * in the current kernel. We stitch up a pte, similar to kmap_atomic.
  */
-ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
-			size_t csize, unsigned long offset, int userbuf)
+ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,
+			size_t csize, unsigned long offset)
 {
 	void  *vaddr;
 	phys_addr_t paddr;
@@ -107,10 +95,10 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
 
 	if (memblock_is_region_memory(paddr, csize)) {
 		vaddr = __va(paddr);
-		csize = copy_oldmem_vaddr(vaddr, buf, csize, offset, userbuf);
+		csize = copy_to_iter(vaddr + offset, csize, iter);
 	} else {
 		vaddr = ioremap_cache(paddr, PAGE_SIZE);
-		csize = copy_oldmem_vaddr(vaddr, buf, csize, offset, userbuf);
+		csize = copy_to_iter(vaddr + offset, csize, iter);
 		iounmap(vaddr);
 	}
 
diff --git a/arch/riscv/kernel/crash_dump.c b/arch/riscv/kernel/crash_dump.c
index 86cc0ada5752..f4dffb8c7eb7 100644
--- a/arch/riscv/kernel/crash_dump.c
+++ b/arch/riscv/kernel/crash_dump.c
@@ -20,9 +20,8 @@
  * @buf. If @buf is in userspace, set @userbuf to %1. Returns number of bytes
  * copied or negative error in case of failure.
  */
-ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
-			 size_t csize, unsigned long offset,
-			 int userbuf)
+ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,
+			 size_t csize, unsigned long offset)
 {
 	void *vaddr;
 
@@ -33,13 +32,7 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
 	if (!vaddr)
 		return -ENOMEM;
 
-	if (userbuf) {
-		if (copy_to_user((char __user *)buf, vaddr + offset, csize)) {
-			memunmap(vaddr);
-			return -EFAULT;
-		}
-	} else
-		memcpy(buf, vaddr + offset, csize);
+	csize = copy_to_iter(vaddr + offset, csize, iter);
 
 	memunmap(vaddr);
 	return csize;
diff --git a/arch/s390/kernel/crash_dump.c b/arch/s390/kernel/crash_dump.c
index 785d54c9350c..09bf559f2c5b 100644
--- a/arch/s390/kernel/crash_dump.c
+++ b/arch/s390/kernel/crash_dump.c
@@ -214,8 +214,8 @@ static int copy_oldmem_user(void __user *dst, void *src, size_t count)
 /*
  * Copy one page from "oldmem"
  */
-ssize_t copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
-			 unsigned long offset, int userbuf)
+ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn, size_t csize,
+			 unsigned long offset)
 {
 	void *src;
 	int rc;
@@ -223,10 +223,12 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
 	if (!csize)
 		return 0;
 	src = (void *) (pfn << PAGE_SHIFT) + offset;
-	if (userbuf)
-		rc = copy_oldmem_user((void __force __user *) buf, src, csize);
+
+	/* XXX: pass the iov_iter down to a common function */
+	if (iter_is_iovec(iter))
+		rc = copy_oldmem_user(iter->iov->iov_base, src, csize);
 	else
-		rc = copy_oldmem_kernel((void *) buf, src, csize);
+		rc = copy_oldmem_kernel(iter->kvec->iov_base, src, csize);
 	return rc;
 }
 
diff --git a/arch/sh/kernel/crash_dump.c b/arch/sh/kernel/crash_dump.c
index 5b41b59698c1..26081861cb62 100644
--- a/arch/sh/kernel/crash_dump.c
+++ b/arch/sh/kernel/crash_dump.c
@@ -23,8 +23,8 @@
  * Copy a page from "oldmem". For this page, there is no pte mapped
  * in the current kernel. We stitch up a pte, similar to kmap_atomic.
  */
-ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
-                               size_t csize, unsigned long offset, int userbuf)
+ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,
+                               size_t csize, unsigned long offset)
 {
 	void  __iomem *vaddr;
 
@@ -32,15 +32,8 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
 		return 0;
 
 	vaddr = ioremap(pfn << PAGE_SHIFT, PAGE_SIZE);
-
-	if (userbuf) {
-		if (copy_to_user((void __user *)buf, (vaddr + offset), csize)) {
-			iounmap(vaddr);
-			return -EFAULT;
-		}
-	} else
-	memcpy(buf, (vaddr + offset), csize);
-
+	csize = copy_to_iter(vaddr + offset, csize, iter);
 	iounmap(vaddr);
+
 	return csize;
 }
diff --git a/arch/x86/kernel/crash_dump_32.c b/arch/x86/kernel/crash_dump_32.c
index 5fcac46aaf6b..23d38ecf5de2 100644
--- a/arch/x86/kernel/crash_dump_32.c
+++ b/arch/x86/kernel/crash_dump_32.c
@@ -42,8 +42,8 @@ static inline bool is_crashed_pfn_valid(unsigned long pfn)
  * Copy a page from "oldmem". For this page, there might be no pte mapped
  * in the current kernel.
  */
-ssize_t copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
-			 unsigned long offset, int userbuf)
+ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn, size_t csize,
+			 unsigned long offset)
 {
 	void  *vaddr;
 
@@ -54,14 +54,7 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
 		return -EFAULT;
 
 	vaddr = kmap_local_pfn(pfn);
-
-	if (!userbuf) {
-		memcpy(buf, vaddr + offset, csize);
-	} else {
-		if (copy_to_user(buf, vaddr + offset, csize))
-			csize = -EFAULT;
-	}
-
+	csize = copy_to_iter(vaddr + offset, csize, iter);
 	kunmap_local(vaddr);
 
 	return csize;
diff --git a/arch/x86/kernel/crash_dump_64.c b/arch/x86/kernel/crash_dump_64.c
index a7f617a3981d..8d91e5f2e14d 100644
--- a/arch/x86/kernel/crash_dump_64.c
+++ b/arch/x86/kernel/crash_dump_64.c
@@ -12,8 +12,8 @@
 #include <linux/io.h>
 #include <linux/cc_platform.h>
 
-static ssize_t __copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
-				  unsigned long offset, int userbuf,
+static ssize_t __copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,
+				  size_t csize, unsigned long offset, 
 				  bool encrypted)
 {
 	void  *vaddr;
@@ -29,13 +29,7 @@ static ssize_t __copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
 	if (!vaddr)
 		return -ENOMEM;
 
-	if (userbuf) {
-		if (copy_to_user((void __user *)buf, vaddr + offset, csize)) {
-			iounmap((void __iomem *)vaddr);
-			return -EFAULT;
-		}
-	} else
-		memcpy(buf, vaddr + offset, csize);
+	csize = copy_to_iter(vaddr + offset, csize, iter);
 
 	set_iounmap_nonlazy();
 	iounmap((void __iomem *)vaddr);
@@ -55,10 +49,10 @@ static ssize_t __copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
  * Copy a page from the old kernel's memory. For this page, there is no pte
  * mapped in the current kernel. We stitch up a pte, similar to kmap_atomic.
  */
-ssize_t copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
-			 unsigned long offset, int userbuf)
+ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn, size_t csize,
+			 unsigned long offset)
 {
-	return __copy_oldmem_page(pfn, buf, csize, offset, userbuf, false);
+	return __copy_oldmem_page(iter, pfn, csize, offset, false);
 }
 
 /**
@@ -66,10 +60,10 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf, size_t csize,
  * memory with the encryption mask set to accommodate kdump on SME-enabled
  * machines.
  */
-ssize_t copy_oldmem_page_encrypted(unsigned long pfn, char *buf, size_t csize,
-				   unsigned long offset, int userbuf)
+ssize_t copy_oldmem_page_encrypted(struct iov_iter *iter, unsigned long pfn,
+				   size_t csize, unsigned long offset)
 {
-	return __copy_oldmem_page(pfn, buf, csize, offset, userbuf, true);
+	return __copy_oldmem_page(iter, pfn, csize, offset, true);
 }
 
 ssize_t elfcorehdr_read(char *buf, size_t count, u64 *ppos)
diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index 509f85148fee..049bafe9c007 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -132,9 +132,8 @@ static int open_vmcore(struct inode *inode, struct file *file)
 }
 
 /* Reads a page from the oldmem device from given offset. */
-ssize_t read_from_oldmem(char *buf, size_t count,
-			 u64 *ppos, int userbuf,
-			 bool encrypted)
+ssize_t read_from_oldmem_iter(struct iov_iter *iter, size_t count,
+			 u64 *ppos, bool encrypted)
 {
 	unsigned long pfn, offset;
 	size_t nr_bytes;
@@ -155,29 +154,23 @@ ssize_t read_from_oldmem(char *buf, size_t count,
 
 		/* If pfn is not ram, return zeros for sparse dump files */
 		if (!pfn_is_ram(pfn)) {
-			tmp = 0;
-			if (!userbuf)
-				memset(buf, 0, nr_bytes);
-			else if (clear_user(buf, nr_bytes))
-				tmp = -EFAULT;
+			tmp = iov_iter_zero(nr_bytes, iter);
 		} else {
 			if (encrypted)
-				tmp = copy_oldmem_page_encrypted(pfn, buf,
+				tmp = copy_oldmem_page_encrypted(iter, pfn,
 								 nr_bytes,
-								 offset,
-								 userbuf);
+								 offset);
 			else
-				tmp = copy_oldmem_page(pfn, buf, nr_bytes,
-						       offset, userbuf);
+				tmp = copy_oldmem_page(iter, pfn, nr_bytes,
+						       offset);
 		}
-		if (tmp < 0) {
+		if (tmp < nr_bytes) {
 			up_read(&vmcore_cb_rwsem);
-			return tmp;
+			return -EFAULT;
 		}
 
 		*ppos += nr_bytes;
 		count -= nr_bytes;
-		buf += nr_bytes;
 		read += nr_bytes;
 		++pfn;
 		offset = 0;
@@ -187,6 +180,27 @@ ssize_t read_from_oldmem(char *buf, size_t count,
 	return read;
 }
 
+ssize_t read_from_oldmem(char *buf, size_t count,
+			 u64 *ppos, int userbuf,
+			 bool encrypted)
+{
+	struct iov_iter iter;
+	struct iovec iov;
+	struct kvec kvec;
+
+	if (userbuf) {
+		iov.iov_base = (__force void __user *)buf;
+		iov.iov_len = count;
+		iov_iter_init(&iter, READ, &iov, 1, count);
+	} else {
+		kvec.iov_base = buf;
+		kvec.iov_len = count;
+		iov_iter_kvec(&iter, READ, &kvec, 1, count);
+	}
+
+	return read_from_oldmem_iter(&iter, count, ppos, encrypted);
+}
+
 /*
  * Architectures may override this function to allocate ELF header in 2nd kernel
  */
@@ -231,11 +245,10 @@ int __weak remap_oldmem_pfn_range(struct vm_area_struct *vma,
 /*
  * Architectures which support memory encryption override this.
  */
-ssize_t __weak
-copy_oldmem_page_encrypted(unsigned long pfn, char *buf, size_t csize,
-			   unsigned long offset, int userbuf)
+ssize_t __weak copy_oldmem_page_encrypted(struct iov_iter *iter,
+		unsigned long pfn, size_t csize, unsigned long offset)
 {
-	return copy_oldmem_page(pfn, buf, csize, offset, userbuf);
+	return copy_oldmem_page(iter, pfn, csize, offset);
 }
 
 /*
diff --git a/include/linux/crash_dump.h b/include/linux/crash_dump.h
index 620821549b23..a1cf7d5c03c7 100644
--- a/include/linux/crash_dump.h
+++ b/include/linux/crash_dump.h
@@ -24,11 +24,10 @@ extern int remap_oldmem_pfn_range(struct vm_area_struct *vma,
 				  unsigned long from, unsigned long pfn,
 				  unsigned long size, pgprot_t prot);
 
-extern ssize_t copy_oldmem_page(unsigned long, char *, size_t,
-						unsigned long, int);
-extern ssize_t copy_oldmem_page_encrypted(unsigned long pfn, char *buf,
-					  size_t csize, unsigned long offset,
-					  int userbuf);
+ssize_t copy_oldmem_page(struct iov_iter *i, unsigned long pfn, size_t csize,
+		unsigned long offset);
+ssize_t copy_oldmem_page_encrypted(struct iov_iter *iter, unsigned long pfn,
+				   size_t csize, unsigned long offset);
 
 void vmcore_cleanup(void);
 
-- 
2.33.0

[PATCH 2/3] vmcore: Convert __read_vmcore to use an iov_iter

[Matthew Wilcox (Oracle)]

This gets rid of copy_to() and let us use proc_read_iter() instead
of proc_read().

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 fs/proc/vmcore.c | 83 ++++++++++++++++++------------------------------
 1 file changed, 31 insertions(+), 52 deletions(-)

diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index 049bafe9c007..443cbaf16ec8 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -251,22 +251,8 @@ ssize_t __weak copy_oldmem_page_encrypted(struct iov_iter *iter,
 	return copy_oldmem_page(iter, pfn, csize, offset);
 }
 
-/*
- * Copy to either kernel or user space
- */
-static int copy_to(void *target, void *src, size_t size, int userbuf)
-{
-	if (userbuf) {
-		if (copy_to_user((char __user *) target, src, size))
-			return -EFAULT;
-	} else {
-		memcpy(target, src, size);
-	}
-	return 0;
-}
-
 #ifdef CONFIG_PROC_VMCORE_DEVICE_DUMP
-static int vmcoredd_copy_dumps(void *dst, u64 start, size_t size, int userbuf)
+static int vmcoredd_copy_dumps(struct iov_iter *iter, u64 start, size_t size)
 {
 	struct vmcoredd_node *dump;
 	u64 offset = 0;
@@ -279,14 +265,13 @@ static int vmcoredd_copy_dumps(void *dst, u64 start, size_t size, int userbuf)
 		if (start < offset + dump->size) {
 			tsz = min(offset + (u64)dump->size - start, (u64)size);
 			buf = dump->buf + start - offset;
-			if (copy_to(dst, buf, tsz, userbuf)) {
+			if (copy_to_iter(buf, tsz, iter) < tsz) {
 				ret = -EFAULT;
 				goto out_unlock;
 			}
 
 			size -= tsz;
 			start += tsz;
-			dst += tsz;
 
 			/* Leave now if buffer filled already */
 			if (!size)
@@ -342,33 +327,30 @@ static int vmcoredd_mmap_dumps(struct vm_area_struct *vma, unsigned long dst,
 /* Read from the ELF header and then the crash dump. On error, negative value is
  * returned otherwise number of bytes read are returned.
  */
-static ssize_t __read_vmcore(char *buffer, size_t buflen, loff_t *fpos,
-			     int userbuf)
+static ssize_t __read_vmcore(struct iov_iter *iter, loff_t *fpos)
 {
 	ssize_t acc = 0, tmp;
 	size_t tsz;
 	u64 start;
 	struct vmcore *m = NULL;
 
-	if (buflen == 0 || *fpos >= vmcore_size)
+	if (iter->count == 0 || *fpos >= vmcore_size)
 		return 0;
 
-	/* trim buflen to not go beyond EOF */
-	if (buflen > vmcore_size - *fpos)
-		buflen = vmcore_size - *fpos;
+	/* trim iter to not go beyond EOF */
+	if (iter->count > vmcore_size - *fpos)
+		iter->count = vmcore_size - *fpos;
 
 	/* Read ELF core header */
 	if (*fpos < elfcorebuf_sz) {
-		tsz = min(elfcorebuf_sz - (size_t)*fpos, buflen);
-		if (copy_to(buffer, elfcorebuf + *fpos, tsz, userbuf))
+		tsz = min(elfcorebuf_sz - (size_t)*fpos, iter->count);
+		if (copy_to_iter(elfcorebuf + *fpos, tsz, iter) < tsz)
 			return -EFAULT;
-		buflen -= tsz;
 		*fpos += tsz;
-		buffer += tsz;
 		acc += tsz;
 
 		/* leave now if filled buffer already */
-		if (buflen == 0)
+		if (iter->count == 0)
 			return acc;
 	}
 
@@ -389,35 +371,31 @@ static ssize_t __read_vmcore(char *buffer, size_t buflen, loff_t *fpos,
 		/* Read device dumps */
 		if (*fpos < elfcorebuf_sz + vmcoredd_orig_sz) {
 			tsz = min(elfcorebuf_sz + vmcoredd_orig_sz -
-				  (size_t)*fpos, buflen);
+				  (size_t)*fpos, iter->count);
 			start = *fpos - elfcorebuf_sz;
-			if (vmcoredd_copy_dumps(buffer, start, tsz, userbuf))
+			if (vmcoredd_copy_dumps(iter, start, tsz))
 				return -EFAULT;
 
-			buflen -= tsz;
 			*fpos += tsz;
-			buffer += tsz;
 			acc += tsz;
 
 			/* leave now if filled buffer already */
-			if (!buflen)
+			if (!iter->count)
 				return acc;
 		}
 #endif /* CONFIG_PROC_VMCORE_DEVICE_DUMP */
 
 		/* Read remaining elf notes */
-		tsz = min(elfcorebuf_sz + elfnotes_sz - (size_t)*fpos, buflen);
+		tsz = min(elfcorebuf_sz + elfnotes_sz - (size_t)*fpos, iter->count);
 		kaddr = elfnotes_buf + *fpos - elfcorebuf_sz - vmcoredd_orig_sz;
-		if (copy_to(buffer, kaddr, tsz, userbuf))
+		if (copy_to_iter(kaddr, tsz, iter) < tsz)
 			return -EFAULT;
 
-		buflen -= tsz;
 		*fpos += tsz;
-		buffer += tsz;
 		acc += tsz;
 
 		/* leave now if filled buffer already */
-		if (buflen == 0)
+		if (iter->count == 0)
 			return acc;
 	}
 
@@ -425,19 +403,17 @@ static ssize_t __read_vmcore(char *buffer, size_t buflen, loff_t *fpos,
 		if (*fpos < m->offset + m->size) {
 			tsz = (size_t)min_t(unsigned long long,
 					    m->offset + m->size - *fpos,
-					    buflen);
+					    iter->count);
 			start = m->paddr + *fpos - m->offset;
-			tmp = read_from_oldmem(buffer, tsz, &start,
-					       userbuf, cc_platform_has(CC_ATTR_MEM_ENCRYPT));
+			tmp = read_from_oldmem_iter(iter, tsz, &start,
+					cc_platform_has(CC_ATTR_MEM_ENCRYPT));
 			if (tmp < 0)
 				return tmp;
-			buflen -= tsz;
 			*fpos += tsz;
-			buffer += tsz;
 			acc += tsz;
 
 			/* leave now if filled buffer already */
-			if (buflen == 0)
+			if (iter->count == 0)
 				return acc;
 		}
 	}
@@ -445,15 +421,14 @@ static ssize_t __read_vmcore(char *buffer, size_t buflen, loff_t *fpos,
 	return acc;
 }
 
-static ssize_t read_vmcore(struct file *file, char __user *buffer,
-			   size_t buflen, loff_t *fpos)
+static ssize_t read_vmcore(struct kiocb *iocb, struct iov_iter *iter)
 {
-	return __read_vmcore((__force char *) buffer, buflen, fpos, 1);
+	return __read_vmcore(iter, &iocb->ki_pos);
 }
 
 /*
  * The vmcore fault handler uses the page cache and fills data using the
- * standard __vmcore_read() function.
+ * standard __read_vmcore() function.
  *
  * On s390 the fault handler is used for memory regions that can't be mapped
  * directly with remap_pfn_range().
@@ -463,9 +438,10 @@ static vm_fault_t mmap_vmcore_fault(struct vm_fault *vmf)
 #ifdef CONFIG_S390
 	struct address_space *mapping = vmf->vma->vm_file->f_mapping;
 	pgoff_t index = vmf->pgoff;
+	struct iov_iter iter;
+	struct kvec kvec;
 	struct page *page;
 	loff_t offset;
-	char *buf;
 	int rc;
 
 	page = find_or_create_page(mapping, index, GFP_KERNEL);
@@ -473,8 +449,11 @@ static vm_fault_t mmap_vmcore_fault(struct vm_fault *vmf)
 		return VM_FAULT_OOM;
 	if (!PageUptodate(page)) {
 		offset = (loff_t) index << PAGE_SHIFT;
-		buf = __va((page_to_pfn(page) << PAGE_SHIFT));
-		rc = __read_vmcore(buf, PAGE_SIZE, &offset, 0);
+		kvec.iov_base = page_address(page);
+		kvec.iov_len = PAGE_SIZE;
+		iov_iter_kvec(&iter, READ, &kvec, 1, PAGE_SIZE);
+
+		rc = __read_vmcore(&iter, &offset);
 		if (rc < 0) {
 			unlock_page(page);
 			put_page(page);
@@ -724,7 +703,7 @@ static int mmap_vmcore(struct file *file, struct vm_area_struct *vma)
 
 static const struct proc_ops vmcore_proc_ops = {
 	.proc_open	= open_vmcore,
-	.proc_read	= read_vmcore,
+	.proc_read_iter	= read_vmcore,
 	.proc_lseek	= default_llseek,
 	.proc_mmap	= mmap_vmcore,
 };
-- 
2.33.0

[PATCH 3/3] vmcore: Convert read_from_oldmem() to take an iov_iter

[Matthew Wilcox (Oracle)]

Remove the read_from_oldmem() wrapper introduced earlier and convert
all the remaining callers to pass an iov_iter.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 arch/x86/kernel/crash_dump_64.c |  7 +++++-
 fs/proc/vmcore.c                | 40 +++++++++++++--------------------
 include/linux/crash_dump.h      | 10 ++++-----
 3 files changed, 25 insertions(+), 32 deletions(-)

diff --git a/arch/x86/kernel/crash_dump_64.c b/arch/x86/kernel/crash_dump_64.c
index 8d91e5f2e14d..991e09b80852 100644
--- a/arch/x86/kernel/crash_dump_64.c
+++ b/arch/x86/kernel/crash_dump_64.c
@@ -68,6 +68,11 @@ ssize_t copy_oldmem_page_encrypted(struct iov_iter *iter, unsigned long pfn,
 
 ssize_t elfcorehdr_read(char *buf, size_t count, u64 *ppos)
 {
-	return read_from_oldmem(buf, count, ppos, 0,
+	struct kvec kvec = { .iov_base = buf, .iov_len = count };
+	struct iov_iter iter;
+
+	iov_iter_kvec(&iter, READ, &kvec, 1, count);
+
+	return read_from_oldmem(&iter, count, ppos,
 				cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT));
 }
diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index 443cbaf16ec8..986474f02a02 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -132,7 +132,7 @@ static int open_vmcore(struct inode *inode, struct file *file)
 }
 
 /* Reads a page from the oldmem device from given offset. */
-ssize_t read_from_oldmem_iter(struct iov_iter *iter, size_t count,
+ssize_t read_from_oldmem(struct iov_iter *iter, size_t count,
 			 u64 *ppos, bool encrypted)
 {
 	unsigned long pfn, offset;
@@ -180,27 +180,6 @@ ssize_t read_from_oldmem_iter(struct iov_iter *iter, size_t count,
 	return read;
 }
 
-ssize_t read_from_oldmem(char *buf, size_t count,
-			 u64 *ppos, int userbuf,
-			 bool encrypted)
-{
-	struct iov_iter iter;
-	struct iovec iov;
-	struct kvec kvec;
-
-	if (userbuf) {
-		iov.iov_base = (__force void __user *)buf;
-		iov.iov_len = count;
-		iov_iter_init(&iter, READ, &iov, 1, count);
-	} else {
-		kvec.iov_base = buf;
-		kvec.iov_len = count;
-		iov_iter_kvec(&iter, READ, &kvec, 1, count);
-	}
-
-	return read_from_oldmem_iter(&iter, count, ppos, encrypted);
-}
-
 /*
  * Architectures may override this function to allocate ELF header in 2nd kernel
  */
@@ -220,7 +199,12 @@ void __weak elfcorehdr_free(unsigned long long addr)
  */
 ssize_t __weak elfcorehdr_read(char *buf, size_t count, u64 *ppos)
 {
-	return read_from_oldmem(buf, count, ppos, 0, false);
+	struct kvec kvec = { .iov_base = buf, .iov_len = count };
+	struct iov_iter iter;
+
+	iov_iter_kvec(&iter, READ, &kvec, 1, count);
+
+	return read_from_oldmem(&iter, count, ppos, false);
 }
 
 /*
@@ -228,7 +212,13 @@ ssize_t __weak elfcorehdr_read(char *buf, size_t count, u64 *ppos)
  */
 ssize_t __weak elfcorehdr_read_notes(char *buf, size_t count, u64 *ppos)
 {
-	return read_from_oldmem(buf, count, ppos, 0, cc_platform_has(CC_ATTR_MEM_ENCRYPT));
+	struct kvec kvec = { .iov_base = buf, .iov_len = count };
+	struct iov_iter iter;
+
+	iov_iter_kvec(&iter, READ, &kvec, 1, count);
+
+	return read_from_oldmem(&iter, count, ppos,
+			cc_platform_has(CC_ATTR_MEM_ENCRYPT));
 }
 
 /*
@@ -405,7 +395,7 @@ static ssize_t __read_vmcore(struct iov_iter *iter, loff_t *fpos)
 					    m->offset + m->size - *fpos,
 					    iter->count);
 			start = m->paddr + *fpos - m->offset;
-			tmp = read_from_oldmem_iter(iter, tsz, &start,
+			tmp = read_from_oldmem(iter, tsz, &start,
 					cc_platform_has(CC_ATTR_MEM_ENCRYPT));
 			if (tmp < 0)
 				return tmp;
diff --git a/include/linux/crash_dump.h b/include/linux/crash_dump.h
index a1cf7d5c03c7..0f3a656293b0 100644
--- a/include/linux/crash_dump.h
+++ b/include/linux/crash_dump.h
@@ -134,13 +134,11 @@ static inline int vmcore_add_device_dump(struct vmcoredd_data *data)
 #endif /* CONFIG_PROC_VMCORE_DEVICE_DUMP */
 
 #ifdef CONFIG_PROC_VMCORE
-ssize_t read_from_oldmem(char *buf, size_t count,
-			 u64 *ppos, int userbuf,
-			 bool encrypted);
+ssize_t read_from_oldmem(struct iov_iter *iter, size_t count,
+			 u64 *ppos, bool encrypted);
 #else
-static inline ssize_t read_from_oldmem(char *buf, size_t count,
-				       u64 *ppos, int userbuf,
-				       bool encrypted)
+static inline ssize_t read_from_oldmem(struct iov_iter *iter, size_t count,
+				       u64 *ppos, bool encrypted)
 {
 	return -EOPNOTSUPP;
 }
-- 
2.33.0

Re: [PATCH 1/3] vmcore: Convert copy_oldmem_page() to take an iov_iter

[Matthew Wilcox]

On Mon, Dec 13, 2021 at 12:06:34AM +0000, Matthew Wilcox (Oracle) wrote:
> +++ b/arch/arm/kernel/crash_dump.c
> @@ -27,9 +27,8 @@
>   * @buf. If @buf is in userspace, set @userbuf to %1. Returns number of bytes
>   * copied or negative error in case of failure.
>   */
> -ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
> -			 size_t csize, unsigned long offset,
> -			 int userbuf)
> +ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,
> +			 size_t csize, unsigned long offset)
>  {
>  	void *vaddr;
>  

I forgot to mention that I didn't adjust the kernel-doc.  I'm tempted to
remove it entirely, to be honest.  It's not included into the rst files,
and having the documentation repeated ten times across arch directories
isn't useful.

Re: [PATCH 1/3] vmcore: Convert copy_oldmem_page() to take an iov_iter

[kernel test robot]

Hi "Matthew,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on tip/x86/core]
[also build test ERROR on arm64/for-next/core powerpc/next s390/features linus/master v5.16-rc5]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Matthew-Wilcox-Oracle/Convert-vmcore-to-use-an-iov_iter/20211213-080748
base:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git e463a09af2f0677b9485a7e8e4e70b396b2ffb6f
config: riscv-randconfig-r012-20211213 (https://download.01.org/0day-ci/archive/20211213/202112131020.pSJ77Cjj-lkp@intel.com/config)
compiler: riscv64-linux-gcc (GCC) 11.2.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/0day-ci/linux/commit/e1684ad72e2cce57ac90ae1270668753f1aa6c60
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Matthew-Wilcox-Oracle/Convert-vmcore-to-use-an-iov_iter/20211213-080748
        git checkout e1684ad72e2cce57ac90ae1270668753f1aa6c60
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=riscv SHELL=/bin/bash arch/riscv/kernel/ fs/proc/

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   arch/riscv/kernel/crash_dump.c: In function 'copy_oldmem_page':
>> arch/riscv/kernel/crash_dump.c:35:17: error: implicit declaration of function 'copy_to_iter'; did you mean 'copy_to_user'? [-Werror=implicit-function-declaration]
      35 |         csize = copy_to_iter(vaddr + offset, csize, iter);
         |                 ^~~~~~~~~~~~
         |                 copy_to_user
   cc1: some warnings being treated as errors
--
   fs/proc/vmcore.c:135:9: warning: no previous prototype for 'read_from_oldmem_iter' [-Wmissing-prototypes]
     135 | ssize_t read_from_oldmem_iter(struct iov_iter *iter, size_t count,
         |         ^~~~~~~~~~~~~~~~~~~~~
   fs/proc/vmcore.c: In function 'read_from_oldmem_iter':
>> fs/proc/vmcore.c:157:31: error: implicit declaration of function 'iov_iter_zero' [-Werror=implicit-function-declaration]
     157 |                         tmp = iov_iter_zero(nr_bytes, iter);
         |                               ^~~~~~~~~~~~~
   fs/proc/vmcore.c: In function 'read_from_oldmem':
>> fs/proc/vmcore.c:187:25: error: storage size of 'iter' isn't known
     187 |         struct iov_iter iter;
         |                         ^~~~
   fs/proc/vmcore.c:188:22: error: storage size of 'iov' isn't known
     188 |         struct iovec iov;
         |                      ^~~
>> fs/proc/vmcore.c:189:21: error: storage size of 'kvec' isn't known
     189 |         struct kvec kvec;
         |                     ^~~~
   fs/proc/vmcore.c:194:17: error: implicit declaration of function 'iov_iter_init'; did you mean 'klist_iter_init'? [-Werror=implicit-function-declaration]
     194 |                 iov_iter_init(&iter, READ, &iov, 1, count);
         |                 ^~~~~~~~~~~~~
         |                 klist_iter_init
>> fs/proc/vmcore.c:198:17: error: implicit declaration of function 'iov_iter_kvec' [-Werror=implicit-function-declaration]
     198 |                 iov_iter_kvec(&iter, READ, &kvec, 1, count);
         |                 ^~~~~~~~~~~~~
   fs/proc/vmcore.c:189:21: warning: unused variable 'kvec' [-Wunused-variable]
     189 |         struct kvec kvec;
         |                     ^~~~
   fs/proc/vmcore.c:188:22: warning: unused variable 'iov' [-Wunused-variable]
     188 |         struct iovec iov;
         |                      ^~~
   fs/proc/vmcore.c:187:25: warning: unused variable 'iter' [-Wunused-variable]
     187 |         struct iov_iter iter;
         |                         ^~~~
   fs/proc/vmcore.c:202:1: error: control reaches end of non-void function [-Werror=return-type]
     202 | }
         | ^
   cc1: some warnings being treated as errors


vim +35 arch/riscv/kernel/crash_dump.c

    10	
    11	/**
    12	 * copy_oldmem_page() - copy one page from old kernel memory
    13	 * @pfn: page frame number to be copied
    14	 * @buf: buffer where the copied page is placed
    15	 * @csize: number of bytes to copy
    16	 * @offset: offset in bytes into the page
    17	 * @userbuf: if set, @buf is in a user address space
    18	 *
    19	 * This function copies one page from old kernel memory into buffer pointed by
    20	 * @buf. If @buf is in userspace, set @userbuf to %1. Returns number of bytes
    21	 * copied or negative error in case of failure.
    22	 */
    23	ssize_t copy_oldmem_page(struct iov_iter *iter, unsigned long pfn,
    24				 size_t csize, unsigned long offset)
    25	{
    26		void *vaddr;
    27	
    28		if (!csize)
    29			return 0;
    30	
    31		vaddr = memremap(__pfn_to_phys(pfn), PAGE_SIZE, MEMREMAP_WB);
    32		if (!vaddr)
    33			return -ENOMEM;
    34	
  > 35		csize = copy_to_iter(vaddr + offset, csize, iter);

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

Re: [PATCH 2/3] vmcore: Convert __read_vmcore to use an iov_iter

[kernel test robot]

Hi "Matthew,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on tip/x86/core]
[also build test ERROR on arm64/for-next/core powerpc/next s390/features linus/master v5.16-rc5]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Matthew-Wilcox-Oracle/Convert-vmcore-to-use-an-iov_iter/20211213-080748
base:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git e463a09af2f0677b9485a7e8e4e70b396b2ffb6f
config: riscv-randconfig-r012-20211213 (https://download.01.org/0day-ci/archive/20211213/202112131103.3ExA0BMN-lkp@intel.com/config)
compiler: riscv64-linux-gcc (GCC) 11.2.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/0day-ci/linux/commit/687563a8e516282784ed87ca7ed3eca900b42192
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Matthew-Wilcox-Oracle/Convert-vmcore-to-use-an-iov_iter/20211213-080748
        git checkout 687563a8e516282784ed87ca7ed3eca900b42192
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=riscv SHELL=/bin/bash fs/proc/

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   fs/proc/vmcore.c:135:9: warning: no previous prototype for 'read_from_oldmem_iter' [-Wmissing-prototypes]
     135 | ssize_t read_from_oldmem_iter(struct iov_iter *iter, size_t count,
         |         ^~~~~~~~~~~~~~~~~~~~~
   fs/proc/vmcore.c: In function 'read_from_oldmem_iter':
   fs/proc/vmcore.c:157:31: error: implicit declaration of function 'iov_iter_zero' [-Werror=implicit-function-declaration]
     157 |                         tmp = iov_iter_zero(nr_bytes, iter);
         |                               ^~~~~~~~~~~~~
   fs/proc/vmcore.c: In function 'read_from_oldmem':
   fs/proc/vmcore.c:187:25: error: storage size of 'iter' isn't known
     187 |         struct iov_iter iter;
         |                         ^~~~
   fs/proc/vmcore.c:188:22: error: storage size of 'iov' isn't known
     188 |         struct iovec iov;
         |                      ^~~
   fs/proc/vmcore.c:189:21: error: storage size of 'kvec' isn't known
     189 |         struct kvec kvec;
         |                     ^~~~
   fs/proc/vmcore.c:194:17: error: implicit declaration of function 'iov_iter_init'; did you mean 'klist_iter_init'? [-Werror=implicit-function-declaration]
     194 |                 iov_iter_init(&iter, READ, &iov, 1, count);
         |                 ^~~~~~~~~~~~~
         |                 klist_iter_init
   fs/proc/vmcore.c:198:17: error: implicit declaration of function 'iov_iter_kvec' [-Werror=implicit-function-declaration]
     198 |                 iov_iter_kvec(&iter, READ, &kvec, 1, count);
         |                 ^~~~~~~~~~~~~
   fs/proc/vmcore.c:189:21: warning: unused variable 'kvec' [-Wunused-variable]
     189 |         struct kvec kvec;
         |                     ^~~~
   fs/proc/vmcore.c:188:22: warning: unused variable 'iov' [-Wunused-variable]
     188 |         struct iovec iov;
         |                      ^~~
   fs/proc/vmcore.c:187:25: warning: unused variable 'iter' [-Wunused-variable]
     187 |         struct iov_iter iter;
         |                         ^~~~
   fs/proc/vmcore.c: In function '__read_vmcore':
>> fs/proc/vmcore.c:337:17: error: invalid use of undefined type 'struct iov_iter'
     337 |         if (iter->count == 0 || *fpos >= vmcore_size)
         |                 ^~
   fs/proc/vmcore.c:341:17: error: invalid use of undefined type 'struct iov_iter'
     341 |         if (iter->count > vmcore_size - *fpos)
         |                 ^~
   fs/proc/vmcore.c:342:21: error: invalid use of undefined type 'struct iov_iter'
     342 |                 iter->count = vmcore_size - *fpos;
         |                     ^~
   In file included from include/linux/kernel.h:17,
                    from include/linux/cpumask.h:10,
                    from include/linux/smp.h:13,
                    from include/linux/lockdep.h:14,
                    from include/linux/spinlock.h:62,
                    from include/linux/mmzone.h:8,
                    from include/linux/gfp.h:6,
                    from include/linux/mm.h:10,
                    from fs/proc/vmcore.c:11:
   fs/proc/vmcore.c:346:62: error: invalid use of undefined type 'struct iov_iter'
     346 |                 tsz = min(elfcorebuf_sz - (size_t)*fpos, iter->count);
         |                                                              ^~
   include/linux/minmax.h:20:46: note: in definition of macro '__typecheck'
      20 |         (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
         |                                              ^
   include/linux/minmax.h:36:31: note: in expansion of macro '__safe_cmp'
      36 |         __builtin_choose_expr(__safe_cmp(x, y), \
         |                               ^~~~~~~~~~
   include/linux/minmax.h:45:25: note: in expansion of macro '__careful_cmp'
      45 | #define min(x, y)       __careful_cmp(x, y, <)
         |                         ^~~~~~~~~~~~~
   fs/proc/vmcore.c:346:23: note: in expansion of macro 'min'
     346 |                 tsz = min(elfcorebuf_sz - (size_t)*fpos, iter->count);
         |                       ^~~
   In file included from arch/riscv/include/asm/bug.h:10,
                    from include/linux/bug.h:5,
                    from include/linux/mmdebug.h:5,
                    from include/linux/mm.h:9,
                    from fs/proc/vmcore.c:11:
   fs/proc/vmcore.c:346:62: error: invalid use of undefined type 'struct iov_iter'
     346 |                 tsz = min(elfcorebuf_sz - (size_t)*fpos, iter->count);
         |                                                              ^~
   include/linux/const.h:12:55: note: in definition of macro '__is_constexpr'
      12 |         (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
         |                                                       ^
   include/linux/minmax.h:26:39: note: in expansion of macro '__no_side_effects'
      26 |                 (__typecheck(x, y) && __no_side_effects(x, y))
         |                                       ^~~~~~~~~~~~~~~~~
   include/linux/minmax.h:36:31: note: in expansion of macro '__safe_cmp'
      36 |         __builtin_choose_expr(__safe_cmp(x, y), \
         |                               ^~~~~~~~~~
   include/linux/minmax.h:45:25: note: in expansion of macro '__careful_cmp'
      45 | #define min(x, y)       __careful_cmp(x, y, <)
         |                         ^~~~~~~~~~~~~
   fs/proc/vmcore.c:346:23: note: in expansion of macro 'min'
     346 |                 tsz = min(elfcorebuf_sz - (size_t)*fpos, iter->count);
         |                       ^~~
   In file included from include/linux/kernel.h:17,
                    from include/linux/cpumask.h:10,
                    from include/linux/smp.h:13,
                    from include/linux/lockdep.h:14,
                    from include/linux/spinlock.h:62,
                    from include/linux/mmzone.h:8,
                    from include/linux/gfp.h:6,
                    from include/linux/mm.h:10,
                    from fs/proc/vmcore.c:11:
   fs/proc/vmcore.c:346:62: error: invalid use of undefined type 'struct iov_iter'
     346 |                 tsz = min(elfcorebuf_sz - (size_t)*fpos, iter->count);
         |                                                              ^~
   include/linux/minmax.h:28:34: note: in definition of macro '__cmp'
      28 | #define __cmp(x, y, op) ((x) op (y) ? (x) : (y))
         |                                  ^
   include/linux/minmax.h:45:25: note: in expansion of macro '__careful_cmp'
      45 | #define min(x, y)       __careful_cmp(x, y, <)
         |                         ^~~~~~~~~~~~~
   fs/proc/vmcore.c:346:23: note: in expansion of macro 'min'
     346 |                 tsz = min(elfcorebuf_sz - (size_t)*fpos, iter->count);
         |                       ^~~
   fs/proc/vmcore.c:346:62: error: invalid use of undefined type 'struct iov_iter'
     346 |                 tsz = min(elfcorebuf_sz - (size_t)*fpos, iter->count);
         |                                                              ^~
   include/linux/minmax.h:28:46: note: in definition of macro '__cmp'
      28 | #define __cmp(x, y, op) ((x) op (y) ? (x) : (y))
         |                                              ^
   include/linux/minmax.h:45:25: note: in expansion of macro '__careful_cmp'
      45 | #define min(x, y)       __careful_cmp(x, y, <)
         |                         ^~~~~~~~~~~~~
   fs/proc/vmcore.c:346:23: note: in expansion of macro 'min'
     346 |                 tsz = min(elfcorebuf_sz - (size_t)*fpos, iter->count);
         |                       ^~~
   fs/proc/vmcore.c:346:62: error: invalid use of undefined type 'struct iov_iter'
     346 |                 tsz = min(elfcorebuf_sz - (size_t)*fpos, iter->count);
         |                                                              ^~
   include/linux/minmax.h:32:24: note: in definition of macro '__cmp_once'
      32 |                 typeof(y) unique_y = (y);               \
         |                        ^
   include/linux/minmax.h:45:25: note: in expansion of macro '__careful_cmp'
      45 | #define min(x, y)       __careful_cmp(x, y, <)
         |                         ^~~~~~~~~~~~~
   fs/proc/vmcore.c:346:23: note: in expansion of macro 'min'
     346 |                 tsz = min(elfcorebuf_sz - (size_t)*fpos, iter->count);
         |                       ^~~
   fs/proc/vmcore.c:346:62: error: invalid use of undefined type 'struct iov_iter'
     346 |                 tsz = min(elfcorebuf_sz - (size_t)*fpos, iter->count);
         |                                                              ^~
   include/linux/minmax.h:32:39: note: in definition of macro '__cmp_once'
      32 |                 typeof(y) unique_y = (y);               \
         |                                       ^
   include/linux/minmax.h:45:25: note: in expansion of macro '__careful_cmp'
      45 | #define min(x, y)       __careful_cmp(x, y, <)
         |                         ^~~~~~~~~~~~~
   fs/proc/vmcore.c:346:23: note: in expansion of macro 'min'
     346 |                 tsz = min(elfcorebuf_sz - (size_t)*fpos, iter->count);
         |                       ^~~
   include/linux/minmax.h:36:9: error: first argument to '__builtin_choose_expr' not a constant
      36 |         __builtin_choose_expr(__safe_cmp(x, y), \
         |         ^~~~~~~~~~~~~~~~~~~~~
   include/linux/minmax.h:45:25: note: in expansion of macro '__careful_cmp'
      45 | #define min(x, y)       __careful_cmp(x, y, <)
         |                         ^~~~~~~~~~~~~
   fs/proc/vmcore.c:346:23: note: in expansion of macro 'min'
     346 |                 tsz = min(elfcorebuf_sz - (size_t)*fpos, iter->count);
         |                       ^~~
>> fs/proc/vmcore.c:347:21: error: implicit declaration of function 'copy_to_iter'; did you mean 'copy_to_user'? [-Werror=implicit-function-declaration]
     347 |                 if (copy_to_iter(elfcorebuf + *fpos, tsz, iter) < tsz)
         |                     ^~~~~~~~~~~~
         |                     copy_to_user
   fs/proc/vmcore.c:353:25: error: invalid use of undefined type 'struct iov_iter'
     353 |                 if (iter->count == 0)
         |                         ^~
   In file included from include/linux/kernel.h:17,
                    from include/linux/cpumask.h:10,
                    from include/linux/smp.h:13,
                    from include/linux/lockdep.h:14,
                    from include/linux/spinlock.h:62,
                    from include/linux/mmzone.h:8,
                    from include/linux/gfp.h:6,
                    from include/linux/mm.h:10,
                    from fs/proc/vmcore.c:11:
   fs/proc/vmcore.c:389:76: error: invalid use of undefined type 'struct iov_iter'
     389 |                 tsz = min(elfcorebuf_sz + elfnotes_sz - (size_t)*fpos, iter->count);
         |                                                                            ^~
   include/linux/minmax.h:20:46: note: in definition of macro '__typecheck'
      20 |         (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
         |                                              ^
   include/linux/minmax.h:36:31: note: in expansion of macro '__safe_cmp'
      36 |         __builtin_choose_expr(__safe_cmp(x, y), \
         |                               ^~~~~~~~~~
   include/linux/minmax.h:45:25: note: in expansion of macro '__careful_cmp'
      45 | #define min(x, y)       __careful_cmp(x, y, <)
         |                         ^~~~~~~~~~~~~
   fs/proc/vmcore.c:389:23: note: in expansion of macro 'min'
     389 |                 tsz = min(elfcorebuf_sz + elfnotes_sz - (size_t)*fpos, iter->count);
         |                       ^~~
   In file included from arch/riscv/include/asm/bug.h:10,
                    from include/linux/bug.h:5,
                    from include/linux/mmdebug.h:5,
                    from include/linux/mm.h:9,
                    from fs/proc/vmcore.c:11:
   fs/proc/vmcore.c:389:76: error: invalid use of undefined type 'struct iov_iter'
     389 |                 tsz = min(elfcorebuf_sz + elfnotes_sz - (size_t)*fpos, iter->count);
         |                                                                            ^~
   include/linux/const.h:12:55: note: in definition of macro '__is_constexpr'
      12 |         (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
         |                                                       ^
   include/linux/minmax.h:26:39: note: in expansion of macro '__no_side_effects'
      26 |                 (__typecheck(x, y) && __no_side_effects(x, y))
         |                                       ^~~~~~~~~~~~~~~~~
   include/linux/minmax.h:36:31: note: in expansion of macro '__safe_cmp'
      36 |         __builtin_choose_expr(__safe_cmp(x, y), \
         |                               ^~~~~~~~~~
   include/linux/minmax.h:45:25: note: in expansion of macro '__careful_cmp'
      45 | #define min(x, y)       __careful_cmp(x, y, <)
         |                         ^~~~~~~~~~~~~
   fs/proc/vmcore.c:389:23: note: in expansion of macro 'min'
     389 |                 tsz = min(elfcorebuf_sz + elfnotes_sz - (size_t)*fpos, iter->count);
         |                       ^~~
   In file included from include/linux/kernel.h:17,
                    from include/linux/cpumask.h:10,
                    from include/linux/smp.h:13,
                    from include/linux/lockdep.h:14,
                    from include/linux/spinlock.h:62,
                    from include/linux/mmzone.h:8,
                    from include/linux/gfp.h:6,
                    from include/linux/mm.h:10,
                    from fs/proc/vmcore.c:11:
   fs/proc/vmcore.c:389:76: error: invalid use of undefined type 'struct iov_iter'
     389 |                 tsz = min(elfcorebuf_sz + elfnotes_sz - (size_t)*fpos, iter->count);
         |                                                                            ^~
   include/linux/minmax.h:28:34: note: in definition of macro '__cmp'
      28 | #define __cmp(x, y, op) ((x) op (y) ? (x) : (y))
         |                                  ^
   include/linux/minmax.h:45:25: note: in expansion of macro '__careful_cmp'
      45 | #define min(x, y)       __careful_cmp(x, y, <)
         |                         ^~~~~~~~~~~~~
   fs/proc/vmcore.c:389:23: note: in expansion of macro 'min'
     389 |                 tsz = min(elfcorebuf_sz + elfnotes_sz - (size_t)*fpos, iter->count);
         |                       ^~~
   fs/proc/vmcore.c:389:76: error: invalid use of undefined type 'struct iov_iter'
     389 |                 tsz = min(elfcorebuf_sz + elfnotes_sz - (size_t)*fpos, iter->count);
         |                                                                            ^~
   include/linux/minmax.h:28:46: note: in definition of macro '__cmp'
      28 | #define __cmp(x, y, op) ((x) op (y) ? (x) : (y))
         |                                              ^
   include/linux/minmax.h:45:25: note: in expansion of macro '__careful_cmp'
      45 | #define min(x, y)       __careful_cmp(x, y, <)
         |                         ^~~~~~~~~~~~~
   fs/proc/vmcore.c:389:23: note: in expansion of macro 'min'
     389 |                 tsz = min(elfcorebuf_sz + elfnotes_sz - (size_t)*fpos, iter->count);
         |                       ^~~
   fs/proc/vmcore.c:389:76: error: invalid use of undefined type 'struct iov_iter'
     389 |                 tsz = min(elfcorebuf_sz + elfnotes_sz - (size_t)*fpos, iter->count);
         |                                                                            ^~
   include/linux/minmax.h:32:24: note: in definition of macro '__cmp_once'
      32 |                 typeof(y) unique_y = (y);               \
         |                        ^
   include/linux/minmax.h:45:25: note: in expansion of macro '__careful_cmp'
      45 | #define min(x, y)       __careful_cmp(x, y, <)
         |                         ^~~~~~~~~~~~~
   fs/proc/vmcore.c:389:23: note: in expansion of macro 'min'
     389 |                 tsz = min(elfcorebuf_sz + elfnotes_sz - (size_t)*fpos, iter->count);
         |                       ^~~
   fs/proc/vmcore.c:389:76: error: invalid use of undefined type 'struct iov_iter'
     389 |                 tsz = min(elfcorebuf_sz + elfnotes_sz - (size_t)*fpos, iter->count);


vim +337 fs/proc/vmcore.c

   326	
   327	/* Read from the ELF header and then the crash dump. On error, negative value is
   328	 * returned otherwise number of bytes read are returned.
   329	 */
   330	static ssize_t __read_vmcore(struct iov_iter *iter, loff_t *fpos)
   331	{
   332		ssize_t acc = 0, tmp;
   333		size_t tsz;
   334		u64 start;
   335		struct vmcore *m = NULL;
   336	
 > 337		if (iter->count == 0 || *fpos >= vmcore_size)
   338			return 0;
   339	
   340		/* trim iter to not go beyond EOF */
   341		if (iter->count > vmcore_size - *fpos)
   342			iter->count = vmcore_size - *fpos;
   343	
   344		/* Read ELF core header */
   345		if (*fpos < elfcorebuf_sz) {
   346			tsz = min(elfcorebuf_sz - (size_t)*fpos, iter->count);
 > 347			if (copy_to_iter(elfcorebuf + *fpos, tsz, iter) < tsz)
   348				return -EFAULT;
   349			*fpos += tsz;
   350			acc += tsz;
   351	
   352			/* leave now if filled buffer already */
   353			if (iter->count == 0)
   354				return acc;
   355		}
   356	
   357		/* Read Elf note segment */
   358		if (*fpos < elfcorebuf_sz + elfnotes_sz) {
   359			void *kaddr;
   360	
   361			/* We add device dumps before other elf notes because the
   362			 * other elf notes may not fill the elf notes buffer
   363			 * completely and we will end up with zero-filled data
   364			 * between the elf notes and the device dumps. Tools will
   365			 * then try to decode this zero-filled data as valid notes
   366			 * and we don't want that. Hence, adding device dumps before
   367			 * the other elf notes ensure that zero-filled data can be
   368			 * avoided.
   369			 */
   370	#ifdef CONFIG_PROC_VMCORE_DEVICE_DUMP
   371			/* Read device dumps */
   372			if (*fpos < elfcorebuf_sz + vmcoredd_orig_sz) {
   373				tsz = min(elfcorebuf_sz + vmcoredd_orig_sz -
   374					  (size_t)*fpos, iter->count);
   375				start = *fpos - elfcorebuf_sz;
   376				if (vmcoredd_copy_dumps(iter, start, tsz))
   377					return -EFAULT;
   378	
   379				*fpos += tsz;
   380				acc += tsz;
   381	
   382				/* leave now if filled buffer already */
   383				if (!iter->count)
   384					return acc;
   385			}
   386	#endif /* CONFIG_PROC_VMCORE_DEVICE_DUMP */
   387	
   388			/* Read remaining elf notes */
   389			tsz = min(elfcorebuf_sz + elfnotes_sz - (size_t)*fpos, iter->count);
   390			kaddr = elfnotes_buf + *fpos - elfcorebuf_sz - vmcoredd_orig_sz;
   391			if (copy_to_iter(kaddr, tsz, iter) < tsz)
   392				return -EFAULT;
   393	
   394			*fpos += tsz;
   395			acc += tsz;
   396	
   397			/* leave now if filled buffer already */
   398			if (iter->count == 0)
   399				return acc;
   400		}
   401	
   402		list_for_each_entry(m, &vmcore_list, list) {
   403			if (*fpos < m->offset + m->size) {
   404				tsz = (size_t)min_t(unsigned long long,
   405						    m->offset + m->size - *fpos,
   406						    iter->count);
   407				start = m->paddr + *fpos - m->offset;
   408				tmp = read_from_oldmem_iter(iter, tsz, &start,
   409						cc_platform_has(CC_ATTR_MEM_ENCRYPT));
   410				if (tmp < 0)
   411					return tmp;
   412				*fpos += tsz;
   413				acc += tsz;
   414	
   415				/* leave now if filled buffer already */
   416				if (iter->count == 0)
   417					return acc;
   418			}
   419		}
   420	
   421		return acc;
   422	}
   423	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

Re: [PATCH 3/3] vmcore: Convert read_from_oldmem() to take an iov_iter

[kernel test robot]

Hi "Matthew,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on tip/x86/core]
[also build test ERROR on arm64/for-next/core powerpc/next s390/features linus/master v5.16-rc5]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Matthew-Wilcox-Oracle/Convert-vmcore-to-use-an-iov_iter/20211213-080748
base:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git e463a09af2f0677b9485a7e8e4e70b396b2ffb6f
config: riscv-randconfig-r012-20211213 (https://download.01.org/0day-ci/archive/20211213/202112131249.lfVULc7X-lkp@intel.com/config)
compiler: riscv64-linux-gcc (GCC) 11.2.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/0day-ci/linux/commit/22576d6aef6fb4cffad0a4e85953662c147dfe66
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Matthew-Wilcox-Oracle/Convert-vmcore-to-use-an-iov_iter/20211213-080748
        git checkout 22576d6aef6fb4cffad0a4e85953662c147dfe66
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=riscv SHELL=/bin/bash fs/proc/

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All error/warnings (new ones prefixed by >>):

   fs/proc/vmcore.c: In function 'read_from_oldmem':
   fs/proc/vmcore.c:157:31: error: implicit declaration of function 'iov_iter_zero' [-Werror=implicit-function-declaration]
     157 |                         tmp = iov_iter_zero(nr_bytes, iter);
         |                               ^~~~~~~~~~~~~
   fs/proc/vmcore.c: In function 'elfcorehdr_read':
>> fs/proc/vmcore.c:202:16: error: variable 'kvec' has initializer but incomplete type
     202 |         struct kvec kvec = { .iov_base = buf, .iov_len = count };
         |                ^~~~
>> fs/proc/vmcore.c:202:31: error: 'struct kvec' has no member named 'iov_base'
     202 |         struct kvec kvec = { .iov_base = buf, .iov_len = count };
         |                               ^~~~~~~~
>> fs/proc/vmcore.c:202:42: warning: excess elements in struct initializer
     202 |         struct kvec kvec = { .iov_base = buf, .iov_len = count };
         |                                          ^~~
   fs/proc/vmcore.c:202:42: note: (near initialization for 'kvec')
>> fs/proc/vmcore.c:202:48: error: 'struct kvec' has no member named 'iov_len'
     202 |         struct kvec kvec = { .iov_base = buf, .iov_len = count };
         |                                                ^~~~~~~
   fs/proc/vmcore.c:202:58: warning: excess elements in struct initializer
     202 |         struct kvec kvec = { .iov_base = buf, .iov_len = count };
         |                                                          ^~~~~
   fs/proc/vmcore.c:202:58: note: (near initialization for 'kvec')
   fs/proc/vmcore.c:202:21: error: storage size of 'kvec' isn't known
     202 |         struct kvec kvec = { .iov_base = buf, .iov_len = count };
         |                     ^~~~
   fs/proc/vmcore.c:203:25: error: storage size of 'iter' isn't known
     203 |         struct iov_iter iter;
         |                         ^~~~
   fs/proc/vmcore.c:205:9: error: implicit declaration of function 'iov_iter_kvec' [-Werror=implicit-function-declaration]
     205 |         iov_iter_kvec(&iter, READ, &kvec, 1, count);
         |         ^~~~~~~~~~~~~
   fs/proc/vmcore.c:203:25: warning: unused variable 'iter' [-Wunused-variable]
     203 |         struct iov_iter iter;
         |                         ^~~~
   fs/proc/vmcore.c:202:21: warning: unused variable 'kvec' [-Wunused-variable]
     202 |         struct kvec kvec = { .iov_base = buf, .iov_len = count };
         |                     ^~~~
   fs/proc/vmcore.c: In function 'elfcorehdr_read_notes':
   fs/proc/vmcore.c:215:16: error: variable 'kvec' has initializer but incomplete type
     215 |         struct kvec kvec = { .iov_base = buf, .iov_len = count };
         |                ^~~~
   fs/proc/vmcore.c:215:31: error: 'struct kvec' has no member named 'iov_base'
     215 |         struct kvec kvec = { .iov_base = buf, .iov_len = count };
         |                               ^~~~~~~~
   fs/proc/vmcore.c:215:42: warning: excess elements in struct initializer
     215 |         struct kvec kvec = { .iov_base = buf, .iov_len = count };
         |                                          ^~~
   fs/proc/vmcore.c:215:42: note: (near initialization for 'kvec')
   fs/proc/vmcore.c:215:48: error: 'struct kvec' has no member named 'iov_len'
     215 |         struct kvec kvec = { .iov_base = buf, .iov_len = count };
         |                                                ^~~~~~~
   fs/proc/vmcore.c:215:58: warning: excess elements in struct initializer
     215 |         struct kvec kvec = { .iov_base = buf, .iov_len = count };
         |                                                          ^~~~~
   fs/proc/vmcore.c:215:58: note: (near initialization for 'kvec')
   fs/proc/vmcore.c:215:21: error: storage size of 'kvec' isn't known
     215 |         struct kvec kvec = { .iov_base = buf, .iov_len = count };
         |                     ^~~~
   fs/proc/vmcore.c:216:25: error: storage size of 'iter' isn't known
     216 |         struct iov_iter iter;
         |                         ^~~~
   fs/proc/vmcore.c:216:25: warning: unused variable 'iter' [-Wunused-variable]
   fs/proc/vmcore.c:215:21: warning: unused variable 'kvec' [-Wunused-variable]
     215 |         struct kvec kvec = { .iov_base = buf, .iov_len = count };
         |                     ^~~~
   fs/proc/vmcore.c: In function '__read_vmcore':
   fs/proc/vmcore.c:327:17: error: invalid use of undefined type 'struct iov_iter'
     327 |         if (iter->count == 0 || *fpos >= vmcore_size)
         |                 ^~
   fs/proc/vmcore.c:331:17: error: invalid use of undefined type 'struct iov_iter'
     331 |         if (iter->count > vmcore_size - *fpos)
         |                 ^~
   fs/proc/vmcore.c:332:21: error: invalid use of undefined type 'struct iov_iter'
     332 |                 iter->count = vmcore_size - *fpos;
         |                     ^~
   In file included from include/linux/kernel.h:17,
                    from include/linux/cpumask.h:10,
                    from include/linux/smp.h:13,
                    from include/linux/lockdep.h:14,
                    from include/linux/spinlock.h:62,
                    from include/linux/mmzone.h:8,
                    from include/linux/gfp.h:6,
                    from include/linux/mm.h:10,
                    from fs/proc/vmcore.c:11:
   fs/proc/vmcore.c:336:62: error: invalid use of undefined type 'struct iov_iter'
     336 |                 tsz = min(elfcorebuf_sz - (size_t)*fpos, iter->count);
         |                                                              ^~
   include/linux/minmax.h:20:46: note: in definition of macro '__typecheck'
      20 |         (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
         |                                              ^
   include/linux/minmax.h:36:31: note: in expansion of macro '__safe_cmp'
      36 |         __builtin_choose_expr(__safe_cmp(x, y), \
         |                               ^~~~~~~~~~
   include/linux/minmax.h:45:25: note: in expansion of macro '__careful_cmp'
      45 | #define min(x, y)       __careful_cmp(x, y, <)
         |                         ^~~~~~~~~~~~~
   fs/proc/vmcore.c:336:23: note: in expansion of macro 'min'
     336 |                 tsz = min(elfcorebuf_sz - (size_t)*fpos, iter->count);
         |                       ^~~
   In file included from arch/riscv/include/asm/bug.h:10,
                    from include/linux/bug.h:5,
                    from include/linux/mmdebug.h:5,
                    from include/linux/mm.h:9,
                    from fs/proc/vmcore.c:11:
   fs/proc/vmcore.c:336:62: error: invalid use of undefined type 'struct iov_iter'
     336 |                 tsz = min(elfcorebuf_sz - (size_t)*fpos, iter->count);
         |                                                              ^~
   include/linux/const.h:12:55: note: in definition of macro '__is_constexpr'
      12 |         (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
         |                                                       ^
   include/linux/minmax.h:26:39: note: in expansion of macro '__no_side_effects'
      26 |                 (__typecheck(x, y) && __no_side_effects(x, y))
         |                                       ^~~~~~~~~~~~~~~~~
   include/linux/minmax.h:36:31: note: in expansion of macro '__safe_cmp'
      36 |         __builtin_choose_expr(__safe_cmp(x, y), \
         |                               ^~~~~~~~~~


vim +/kvec +202 fs/proc/vmcore.c

   196	
   197	/*
   198	 * Architectures may override this function to read from ELF header
   199	 */
   200	ssize_t __weak elfcorehdr_read(char *buf, size_t count, u64 *ppos)
   201	{
 > 202		struct kvec kvec = { .iov_base = buf, .iov_len = count };
   203		struct iov_iter iter;
   204	
   205		iov_iter_kvec(&iter, READ, &kvec, 1, count);
   206	
   207		return read_from_oldmem(&iter, count, ppos, false);
   208	}
   209	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

Re: [PATCH 1/3] vmcore: Convert copy_oldmem_page() to take an iov_iter

[Christoph Hellwig]

On Mon, Dec 13, 2021 at 12:06:34AM +0000, Matthew Wilcox (Oracle) wrote:
> Instead of passing in a 'buf' and 'userbuf' argument, pass in an iov_iter.
> s390 needs more work to pass the iov_iter down further, or refactor,
> but I'd be more comfortable if someone who can test on s390 did that work.
> 
> It's more convenient to convert the whole of read_from_oldmem() to
> take an iov_iter at the same time, so rename it to read_from_oldmem_iter()
> and add a temporary read_from_oldmem() wrapper that creates an iov_iter.

This looks pretty reasonable.  s390 could use some love from people that
know the code, and yes, the kerneldoc comments should go away.

Re: [PATCH 2/3] vmcore: Convert __read_vmcore to use an iov_iter

[Christoph Hellwig]

On Mon, Dec 13, 2021 at 12:06:35AM +0000, Matthew Wilcox (Oracle) wrote:
> +	/* trim iter to not go beyond EOF */
> +	if (iter->count > vmcore_size - *fpos)
> +		iter->count = vmcore_size - *fpos;

Nit: iov_iter_truncate()

Otherwise this looks good from a cursory view.

Re: [PATCH 3/3] vmcore: Convert read_from_oldmem() to take an iov_iter

[Christoph Hellwig]

>  
>  ssize_t elfcorehdr_read(char *buf, size_t count, u64 *ppos)
>  {
> -	return read_from_oldmem(buf, count, ppos, 0,
> +	struct kvec kvec = { .iov_base = buf, .iov_len = count };
> +	struct iov_iter iter;
> +
> +	iov_iter_kvec(&iter, READ, &kvec, 1, count);
> +
> +	return read_from_oldmem(&iter, count, ppos,
>  				cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT));
>  }

elfcorehdr_read should probably also take an iov_iter while we're at it.

I also don't quite understand why we even need the arch overrides for it,
but that would require some digging into the history of this interface.

Re: [PATCH 3/3] vmcore: Convert read_from_oldmem() to take an iov_iter

[Baoquan He]

On 12/13/21 at 09:02am, Christoph Hellwig wrote:
> >  
> >  ssize_t elfcorehdr_read(char *buf, size_t count, u64 *ppos)
> >  {
> > -	return read_from_oldmem(buf, count, ppos, 0,
> > +	struct kvec kvec = { .iov_base = buf, .iov_len = count };
> > +	struct iov_iter iter;
> > +
> > +	iov_iter_kvec(&iter, READ, &kvec, 1, count);
> > +
> > +	return read_from_oldmem(&iter, count, ppos,
> >  				cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT));
> >  }
> 
> elfcorehdr_read should probably also take an iov_iter while we're at it.
> 
> I also don't quite understand why we even need the arch overrides for it,
> but that would require some digging into the history of this interface.
> 

Below patchset removing sec_active() from generic code added this arch
override on x86_64. Before that, s390 and arm64 have had arch overrides. 
And arm64 says "elfcorehdr_read() is simple as the region is always mapped."
in commit e62aaeac42 "arm64: kdump: provide /proc/vmcore file".

[v3,0/6] Remove x86-specific code from generic headers
https://patchwork.kernel.org/project/linux-fsdevel/cover/20190718032858.28744-1-bauerman@linux.ibm.com/

5cbdaeefb655 s390/mm: Remove sev_active() function
ae7eb82a92fa fs/core/vmcore: Move sev_active() reference to x86 arch code
284e21fab2cf x86, s390/mm: Move sme_active() and sme_me_mask to x86-specific header
e740815a97e2 dma-mapping: Remove dma_check_mask()
47e5d8f9ed34 swiotlb: Remove call to sme_active()
0c9c1d563975 x86, s390: Move ARCH_HAS_MEM_ENCRYPT definition to arch/Kconfig

Re: [PATCH 3/3] vmcore: Convert read_from_oldmem() to take an iov_iter

[Matthew Wilcox]

On Mon, Dec 13, 2021 at 09:02:57AM +0100, Christoph Hellwig wrote:
> >  
> >  ssize_t elfcorehdr_read(char *buf, size_t count, u64 *ppos)
> >  {
> > -	return read_from_oldmem(buf, count, ppos, 0,
> > +	struct kvec kvec = { .iov_base = buf, .iov_len = count };
> > +	struct iov_iter iter;
> > +
> > +	iov_iter_kvec(&iter, READ, &kvec, 1, count);
> > +
> > +	return read_from_oldmem(&iter, count, ppos,
> >  				cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT));
> >  }
> 
> elfcorehdr_read should probably also take an iov_iter while we're at it.

I don't like how that looks.  For example:

@@ -1246,11 +1247,14 @@ static int __init parse_crash_elf64_headers(void)
        int rc=0;
        Elf64_Ehdr ehdr;
        u64 addr;
+       struct iov_iter iter;
+       struct kvec kvec = { .iov_base = &ehdr, .iov_len = sizeof(ehdr) };

        addr = elfcorehdr_addr;

        /* Read Elf header */
-       rc = elfcorehdr_read((char *)&ehdr, sizeof(Elf64_Ehdr), &addr);
+       iov_iter_kvec(&iter, READ, &kvec, 1, sizeof(ehdr));
+       rc = elfcorehdr_read(&iter, &addr);
        if (rc < 0)
                return rc;

@@ -1277,7 +1281,10 @@ static int __init parse_crash_elf64_headers(void)
        if (!elfcorebuf)
                return -ENOMEM;
        addr = elfcorehdr_addr;
-       rc = elfcorehdr_read(elfcorebuf, elfcorebuf_sz_orig, &addr);
+       kvec.iov_base = elfcorebuf;
+       kvec.iov_len = elfcorebuf_sz_orig;
+       iov_iter_kvec(&iter, READ, &kvec, 1, elfcorebuf_sz_orig);
+       rc = elfcorehdr_read(&iter, &addr);
        if (rc < 0)
                goto fail;


I don't think this makes the code clearer, and it's already pretty ugly
code.  I'd rather leave constructing the iov_iter to elfcorehdr_read().
(Same remarks apply to elfcorehdr_read_notes())

> I also don't quite understand why we even need the arch overrides for it,
> but that would require some digging into the history of this interface.

I decided I didn't want to know ;-)

Re: [PATCH 1/3] vmcore: Convert copy_oldmem_page() to take an iov_iter

[Heiko Carstens]

On Mon, Dec 13, 2021 at 08:57:25AM +0100, Christoph Hellwig wrote:
> On Mon, Dec 13, 2021 at 12:06:34AM +0000, Matthew Wilcox (Oracle) wrote:
> > Instead of passing in a 'buf' and 'userbuf' argument, pass in an iov_iter.
> > s390 needs more work to pass the iov_iter down further, or refactor,
> > but I'd be more comfortable if someone who can test on s390 did that work.
> > 
> > It's more convenient to convert the whole of read_from_oldmem() to
> > take an iov_iter at the same time, so rename it to read_from_oldmem_iter()
> > and add a temporary read_from_oldmem() wrapper that creates an iov_iter.
> 
> This looks pretty reasonable.  s390 could use some love from people that
> know the code, and yes, the kerneldoc comments should go away.

Sure, we will take care of this. Added to ToDo list.